Field of the Invention
The present invention relates to honeycomb structures. More particularly the present invention relates to a honeycomb structure with improved thermal shock resistance.
Description of the Related Art
A honeycomb structure has been conventionally known, which serves as a filter to purify exhaust gas emitted from an internal combustion engine of an automobile or the like, and includes a partition wall defining cells as a through channel of the exhaust gas. This filter is to purify exhaust gas by removing harmful substance such as NOx or particulates in the exhaust gas.
For this honeycomb structure, the structure including hexagonal-shaped cells (hexagon cells) at the cross section orthogonal to the extending direction of the cells is known (e.g., see Patent Document 1). Such hexagon cells have catalyst uniformly loaded on the surface of the partition wall defining these hexagon cells, and therefore such cells have high purification performance compared with square cells, and as a result the use thereof has been expanded. Note here that square cells refer to cells having a square shape at the cross section orthogonal to the extending direction of the cells. Recently the use of the honeycomb structure including hexagon cells (hexagon cell honeycomb structure) has been expanded not only for three-way catalyst but also for catalyst to purify NOx. A study has been further conducted for such a hexagon cell honeycomb structure to achieve upsizing or to let it have various shapes (circumferential shapes at the cross section orthogonal to the cell extending direction).